1. Technical Field
The present invention relates generally to a method and apparatus for handling cardboard or paperboard materials. More particularly, the present invention relates to a method and apparatus for handling stacks of paperboard sheets. Specifically, the present invention relates to a method and apparatus for verifying the size of the paperboard sheets.
2. Background Information
Corrugators and other machines for producing and handling corrugated cardboard materials are well known in the art. Corrugators are used to form corrugated paperboard, which minimally includes a wavy or fluted paper known as a corrugated medium which is glued to a flat sheet typically called a liner. Corrugated paperboard can include one or more layers of the corrugated medium and one or more liners. Many boxes are formed of a single wall corrugated board, which is a corrugated medium glued between two flat liners. Corrugated paperboard also includes, for example, double wall corrugated boards and triple wall corrugated boards. The double wall corrugated board includes two layers of corrugated medium with three flat liners, and the triple wall corrugated board includes three layers of corrugated medium and four flat liners. Boxes may also be formed of the double wall and triple wall corrugated boards.
Once the given type of corrugated paperboard is formed by the corrugator, the corrugator or another machine typically cuts the corrugated paperboard into flat rectangular sheets, which are formed into a stack with multiple sheets atop one another. Due to the large variety in sizes of boxes, the length and width dimensions of these paperboard sheets varies correspondingly. A stacking device or stacker is configured to handle multiple different sizes of sheets in a relatively rapid fashion. Thus, the stacker may produce a batch of sheets each having the same dimensions whereby each of the stacks has the same dimensions, then produce a subsequent batch immediately thereafter in which the sheets and stacks have dimensions which are different than the earlier batch. Normally, a stacker operator applies a run sheet or label to each stack which is supposed to correspond to the stack with regard to its dimensions and other relevant information. However, because the formation of the stacks is relatively rapid, and the change from a batch of stacks having a first size to a second batch of stacks having a second size likewise occurs relatively rapidly, it is easy for the stacker operator to inadvertently place the wrong run sheet or label on the stack. If this mistake is not caught and corrected, the incorrectly labeled stack may be shipped to the wrong customer. Thus, there is a need in the art for a method and apparatus for verifying the stack size and ensuring that the proper label is applied so that the stack is shipped to the correct customer. The present invention achieves this goal.